docstr: Test corner case where an network might predict no boxes.
docstr_tok: ["Test","corner","case","where","an","network","might","predict","no","boxes","."]
code: def test_approx_iou_assigner_with_empty_boxes(self):
      """Test corner case where an network might predict no boxes."""
      assigner = ApproxMaxIoUAssigner(
          pos_iou_thr=0.5,
          neg_iou_thr=0.5,
      )
      bboxes = torch.empty((0, 4))
      gt_bboxes = torch.FloatTensor(
          [
              [0, 0, 10, 9],
              [0, 10, 10, 19],
          ]
      )
      gt_labels = torch.LongTensor([2, 3])
  
      pred_instances = InstanceData()
      pred_instances.priors = bboxes
      pred_instances.approxs = bboxes[:, None, :]
      gt_instances = InstanceData()
      gt_instances.bboxes = gt_bboxes
      gt_instances.labels = gt_labels
      assign_result = assigner.assign(pred_instances, gt_instances)
  
      self.assertEqual(len(assign_result.gt_inds), 0)
  
file_path: mmdetection/tests/test_models/test_task_modules/test_assigners/test_approx_max_iou_assigner.py
imports: from unittest import TestCase
  import torch
  from mmengine.structures import InstanceData
  from mmdet.models.task_modules.assigners import ApproxMaxIoUAssigner
label_desc: Use image node_id 3 for calling the TestApproxIoUAssigner obj's underlying member method code with example usage: obj.test_approx_iou_assigner_with_empty_boxes() without return types